Sliding component

ABSTRACT

Provide a sliding component that reduces the leakage rate of sealed fluid and significantly improves the lubrication characteristics at startup or stop, while being actuated by means of fluid lubrication in the rotation phase, thereby achieving the effects of sealing and lubrication at the same time. The sliding component is characterized in that: on one sealing face of a pair of sliding parts that slide relative to each other, multiple positive pressure-generating mechanisms that comprise extremely shallow parallel grooves running roughly in parallel with the sealing face and having submicron-level height differences are provided independently in the circumferential direction; the extremely shallow parallel grooves connect to the high-pressure fluid side, but are isolated from the low-pressure fluid side by a seal area; and extremely shallow thin grooves are formed at the bottom of the extremely shallow parallel grooves.

TECHNICAL FIELD

The present invention relates to a sliding component suitable formechanical seals, bearings, and other sliding mechanisms. In particular,the present invention relates to a sliding component for seal rings,bearings, and other mechanisms where fluid is present on the sealingface to reduce friction and where leakage of fluid from the sealing facemust be prevented.

BACKGROUND ART

With a mechanical seal, which is an example of a sliding component, themutually exclusive conditions of “seal” and “lubricate” must besatisfied simultaneously in order to maintain its sealing performancefor an extended time. Particularly in recent years, to help protect theenvironment, etc., there is a growing need to lower friction further andthereby reduce mechanical loss, while still preventing leakage of thefluid being sealed. Friction can be lowered by creating a so-calledfluid lubrication state, which represents a state of surfaces slidingagainst each other with a liquid film in between, achieved by generatingdynamic pressure between the sealing faces by means of rotation. In thiscase, however, generation of positive pressure between the sealing facescauses the fluid to flow out of the sealing faces from the positivepressure area. This is so-called side leakage that occurs with abearing, which corresponds to leakage in the case of a seal. When thefluid to be sealed is present on the outer periphery side of the sealarea and atmosphere on the inner periphery side, and the fluid on theouter periphery side is sealed in this state (referred to as the “insidetype”), the leakage rate on the inner periphery side is expressed by theformula below:

$\begin{matrix}{Q = {- {\int{\left( \left. {\frac{h^{3}}{12\; \eta}\frac{\partial p}{\partial r}} \right|_{r = r_{1}} \right){r_{1} \cdot {\theta}}}}}} & \left\{ {{Mathematical}\mspace{14mu} {Formula}\mspace{14mu} 1} \right\}\end{matrix}$

Q: Leakage rate on the inner periphery side at the inner diameter r1 ofthe sealing face (The negative sign indicates leakage).

h: Height of clearance

η: Viscosity of fluid

p: Pressure

From the above formula, it is clear that the pressure slope ∂p/∂r at theinner periphery side increases as fluid lubrication is promoted, dynamicpressure generates, and liquid film forms, and as a result of a largerh, the leakage rate Q increases.

In the case of a seal, therefore, the clearance h and pressure slope∂p/∂r must be decreased in order to reduce the leakage rate Q.

As for the friction characteristics of a slide bearing, which aresimilar to those of a mechanical seal, the “Stribeck curve” shown inFIG. 4 is known (Reference Literature: “Tribology” by H. Czichos,Kodansha).

The horizontal axis in FIG. 4 represents “Viscosity η×Velocity v/LoadF_(N),” or simply the velocity if the viscosity and load are constant.If the viscosity and load are constant, the friction coefficient issmall in the medium-speed region or mixed lubrication region “Second: h(clearance)≅R (roughness)” and the high-speed region or fluidlubrication region “First: h (clearance)>>R (roughness),” but thefriction coefficient becomes extremely large at startup in the boundarylubrication region “Third: h (clearance)→0.”

According to the numerical analysis conducted by the inventors named inthe present application for patent, on the other hand, the groove depthon the sealing face and friction coefficient of the sealing face havethe relationship shown in FIG. 5 in the case of a mechanical seal, andthe relationship between the groove depth and friction coefficient ofthe sealing face varies depending on the sliding speed of the sealingface.

Also, generally dynamic pressure-generating grooves are provided on amechanical seal to ensure the mechanical seal is effective in the normalrotational speed region and also to guide sufficient fluid to thesealing face, and these dynamic pressure-generating grooves areprocessed to a depth of several μm or more by means of machining,blasting, or laser. Because of this, low friction is achieved in themedium-speed region and high-speed region, but sufficient load capacitycannot be achieved in the low-speed region, which makes it difficult toachieve low friction in this speed region. Particularly at startup andstop where sufficient dynamic pressure does not generate, sufficientlubrication characteristics are not demonstrated and problems occur as aresult, such as noise and excessive contact between the sealing faces atstartup and stop.

Also in recent years, sliding materials for mechanical seals areproposed that can reduce the friction coefficient without generatingexcessive leakage by introducing the sealed fluid to the space betweenthe sealing faces and holding it there in good condition, including onewhere multiple dynamic pressure-generating grooves are provided in thecircumferential direction to generate dynamic pressure between thesealing faces as a result of one sealing face rotating relative to themating sealing face, wherein the dynamic pressure-generating groovescomprise straight grooves or curved spiral grooves having an angle tothe sliding direction and the dynamic pressure-generating grooves areprocessed to a depth of 1 μm or less by means of femtosecond laser(refer to Patent Literatures 1 and 2, for example).

However, the inventions described in Patent Literatures 1 and 2 aim togenerate dynamic pressure between the sealing faces as a result of onesealing face rotating relative to the mating sealing face, and althoughlow friction is achieved in the medium- and high-speed regions at highpressure, sufficient dynamic pressure is not generated and thussufficient lubrication characteristics cannot be demonstrated in themedium- and high-speed regions at low pressure or at startup and stop,which presents a problem. In addition, the mechanism of introducing thesealed fluid into the space between the sealing faces by the dynamicpressure-generating grooves requires circular grooves or other means forpreventing leakage to be provided on the low-pressure side of thesealing face, in order to reduce the leakage rate.

PRIOR ART LITERATURES Patent Literatures

-   Patent Literature 1: International Patent Laid-open No. 2009/087995-   Patent Literature 2: Japanese Patent Laid-open No. 2011-196429

SUMMARY OF INVENTION Problems to be Solved by Invention

An object of the present invention is to provide a sliding componentthat reduces the leakage rate of sealed fluid and significantly improvesthe lubrication characteristics at startup or stop, while being actuatedby means of fluid lubrication in the rotation phase, thereby achievingthe effects of sealing and lubrication at the same time.

Means to Solve Problems

To achieve the aforementioned object, firstly the sliding componentproposed by the present invention is characterized in that: on onesealing face of a pair of sliding parts that slide relative to eachother, multiple positive pressure-generating mechanisms that compriseextremely shallow parallel grooves running roughly in parallel with thesealing face and having submicron-level height differences are providedindependently in the circumferential direction; the extremely shallowparallel grooves connect to the high-pressure fluid side, but areisolated from the low-pressure fluid side by a seal area; and extremelyshallow thin grooves are formed at the bottom of the extremely shallowparallel grooves.

According to the first feature, the sealed fluid entering the extremelyshallow parallel grooves forms an extremely thin fluid film and theaction of its surface tension increases the pressure region where thefluid can be sealed without increasing leakage, while in the rotationphase the relative sliding of the applicable sealing face with themating sealing face generates dynamic pressure so that the sealing facecan be lifted by the minimum required amount as a result of the dynamicpressure effect, and consequently good lubrication performance can bemaintained without increasing leakage and, in particular, thelubrication characteristics at startup or stop can be improvedsignificantly. Additionally, the flow of fluid in the extremely shallowparallel grooves can be controlled and, for example, by rectifying theflow of fluid in the extremely shallow parallel grooves in an optimaldirection according to the wideness or narrowness of the seal areaformed between the extremely shallow parallel grooves and innerperiphery of the seal area, sufficient design flexibility tosimultaneously achieve improved lubrication characteristics of thesealing face and reduced leakage can be achieved.

In addition to the first feature, secondly, the sliding componentproposed by the present invention is characterized in that the extremelyshallow parallel grooves have a depth h of 10 nm to 1 μm, while theextremely shallow thin grooves have a depth a of 10 nm to 1 μm and pitchp of 1 to 500 μm.

In addition to the second feature, thirdly, the sliding componentproposed by the present invention is characterized in that preferablythe extremely shallow parallel grooves have a depth h of 50 to 500 nm.

According to the second and third features, the lubricationcharacteristics at startup or stop can be further improved significantlywithout increasing leakage.

In addition to any one of the first through third features, fourthly,the sliding component proposed by the present invention is characterizedin that the extremely shallow thin grooves are formed in a mannerinclined by a specified angle relative to the sliding direction of thesealing face.

According to the fourth feature, the fluid can be rectified to be takeninto the extremely shallow parallel grooves or discharged from theextremely shallow parallel grooves and, for example, by setting theinclination direction or angle according to the wideness or narrownessof the seal area formed between the extremely shallow parallel groovesand inner periphery of the seal area, the lubrication characteristics atstartup or stop can be further improved significantly without increasingleakage.

In addition to the fourth feature, fifthly, the sliding componentproposed by the present invention is characterized in that the extremelyshallow thin grooves are formed in such a way that the adjacentextremely shallow thin grooves are oriented symmetrical relative to thesliding direction of the sealing face.

According to the fifth feature, fluid is rectified alternately to thehigh-pressure fluid side or low-pressure fluid side in the adjacentextremely shallow parallel grooves, which is advantageous when thesliding component rotates in both directions.

In addition to any one of the first through third features, sixthly, thesliding component proposed by the present invention is characterized inthat the extremely shallow thin grooves are formed along the diameterdirection.

According to the sixth feature, fluid is rectified to flow in thediameter direction in the extremely shallow parallel grooves, so that itflows into the extremely shallow parallel grooves with ease even atstartup or stop of the sliding component and consequently thelubrication characteristics at startup or stop of the sliding componentcan be improved. From the viewpoint of preventing leakage, thesecharacteristics are suitable when the seal area formed between theextremely shallow parallel grooves and inner periphery of the seal areais wide.

In addition to any one of the first through third features, seventhly,the sliding component proposed by the present invention is characterizedin that the extremely shallow thin grooves are formed along thecircumferential direction.

According to the seventh feature, fluid is rectified to flow in thecircumferential direction in the extremely shallow parallel grooves andtherefore, at startup or stop of the sliding component or in therotation phase, the supply of fluid to the sealing face S positionedbetween the extremely shallow parallel grooves is promoted and thelubrication characteristics improve further as a result. From theviewpoint of preventing leakage, these characteristics can also beapplied when the seal area formed between the extremely shallow parallelgrooves and inner periphery of the seal area is narrow.

In addition to any one of the first through seventh features, eighthly,the sliding component proposed by the present invention is characterizedin that preferably the extremely shallow parallel grooves are providedto account for 5 to 70% of the area of the sealing face.

According to the eighth feature, the surface pressure of the sealingface can be maintained in good condition, while at the same time leakagecan be reduced and the lubrication characteristics at startup or stopcan be improved significantly.

In addition to any of the first through eighth characteristics, ninthly,the sliding component proposed by the present invention is characterizedin that the pair of sliding parts is comprised of ring-shaped bodieseach used as either a stationary-side sliding member or rotating-sidesliding member of a mechanical seal that rotates relative to the othermember.

According to the ninth feature, a mechanical seal that can maintain goodlubrication performance without increasing leakage and alsosignificantly improve the lubrication characteristics at startup or stopcan be obtained. In addition, the flow of fluid in the extremely shallowparallel grooves can be controlled and, for example, by rectifying theflow of fluid in the extremely shallow parallel grooves in an optimaldirection according to the wideness or narrowness of the seal areaformed between the extremely shallow parallel grooves and innerperiphery of the seal area, a mechanical seal offering sufficient designflexibility to simultaneously achieve improved lubricationcharacteristics of the sealing face and reduced leakage can be provided.

Effects of Invention

The present invention has the excellent effects listed below:

(1) On one sealing face of a pair of sliding parts that slide relativeto each other, multiple positive pressure-generating mechanisms thatcomprise extremely shallow parallel grooves running roughly in parallelwith the sealing face and having submicron-level height differences areprovided independently in the circumferential direction; the extremelyshallow parallel grooves connect to the high-pressure fluid side, butare isolated from the low-pressure fluid side by a seal area; andextremely shallow thin grooves are formed at the bottom of the extremelyshallow parallel grooves; and because of the above, the sealed fluidentering the extremely shallow parallel grooves forms an extremely thinfluid film and the action of its surface tension increases the pressureregion where the fluid can be sealed without increasing leakage, whilein the rotation phase the relative sliding of the applicable sealingface with the mating sealing face generates dynamic pressure so that thesealing face can be lifted by the minimum required amount as a result ofthe dynamic pressure effect, and consequently good lubricationperformance can be maintained without increasing leakage and, inparticular, the lubrication characteristics at startup or stop can beimproved significantly. Additionally, the flow of fluid in the extremelyshallow parallel grooves can be controlled and, for example, byrectifying the flow of fluid in the extremely shallow parallel groovesin an optimal direction according to the wideness or narrowness of theseal area formed between the extremely shallow parallel grooves andinner periphery of the seal area, sufficient design flexibility tosimultaneously achieve improved lubrication characteristics of thesealing face and reduced leakage can be achieved.

(2) The extremely shallow thin grooves are formed in a manner inclinedby a specified angle relative to the sliding direction of the sealingface, and accordingly the fluid can be rectified to be taken into theextremely shallow parallel grooves or discharged from the extremelyshallow parallel grooves and, for example, by setting the inclinationdirection or angle according to the wideness or narrowness of the sealarea formed between the extremely shallow parallel grooves and innerperiphery of the seal area, the lubrication characteristics at startupor stop can be further improved significantly without increasingleakage.

Also, the extremely shallow thin grooves are formed in such a way thatthe adjacent extremely shallow thin grooves are oriented symmetricalrelative to the sliding direction of the sealing face, and accordinglyfluid is rectified alternately to the high-pressure fluid side orlow-pressure fluid side in the adjacent extremely shallow parallelgrooves, which is advantageous when the sliding component rotates inboth directions.

(3) The extremely shallow thin grooves are formed along the diameterdirection, and accordingly fluid is rectified to flow in the diameterdirection in the extremely shallow parallel grooves, so that it flowsinto the extremely shallow parallel grooves with ease and consequentlythe lubrication characteristics at startup or stop of the slidingcomponent can be improved. From the viewpoint of preventing leakage,these characteristics are suitable when the seal area formed between theextremely shallow parallel grooves and inner periphery of the seal areais wide.

Also, the extremely shallow thin grooves are formed along thecircumferential direction, and accordingly at startup or stop of thesliding component or in the rotation phase, the supply of fluid to thesealing face S positioned between the extremely shallow parallel groovesis promoted and the lubrication characteristics improve further as aresult. From the viewpoint of preventing leakage, these characteristicsare suitable when the seal area formed between the extremely shallowparallel grooves and inner periphery of the seal area is narrow.

(4) Preferably the extremely shallow parallel grooves are provided toaccount for 5 to 70% of the area of the sealing face, and accordinglythe surface pressure of the sealing face can be kept in good condition,while at the same time leakage can be reduced and the lubricationcharacteristics at startup or stop can be improved significantly.

(5) The pair of sliding parts is comprised of ring-shaped bodies eachused as either a stationary-side sliding member or rotating-side slidingmember of a mechanical seal that rotates relative to the other member,and accordingly a mechanical seal that can maintain good lubricationperformance without increasing leakage and also significantly improvethe lubrication characteristics at startup or stop can be obtained. Inaddition, the flow of fluid in the extremely shallow parallel groovescan be controlled and, for example, by rectifying the flow of fluid inthe extremely shallow parallel grooves in an optimal direction accordingto the wideness or narrowness of the seal area formed between theextremely shallow parallel grooves and inner periphery of the seal area,a mechanical seal offering sufficient design flexibility tosimultaneously achieve improved lubrication characteristics of thesealing face and reduced leakage can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 Drawings explaining the sealing face of a sliding componentpertaining to Embodiment 1 of the present invention, where (a) is a planview of the sealing face, (b) is a section view taken along A-A, (c) isa section view taken along B-B.

FIG. 2 Drawings explaining the dynamic pressure effect, where (a)represents the present invention, while (b) represents prior art.

FIG. 3 Drawings showing the directions of extremely shallow parallelgrooves formed at the bottom of extremely shallow parallel grooves,where (a) shows extremely shallow thin grooves formed in a mannerinclined by a specified angle in the same direction as the slidingdirection of the sealing face, (b) shows adjacent extremely shallow thingrooves formed symmetrical relative to the sliding direction of thesealing face, (c) shows extremely shallow thin grooves formed along thediameter direction, and (d) shows extremely shallow thin grooves formedalong the circumferential direction.

FIG. 4 Drawing explaining the friction characteristics of a bearing,where the horizontal axis represents the bearing characteristic number G(non-dimensional), while the vertical axis represents the frictioncoefficient f.

FIG. 5 Relationship between the depth of grooves on the sealing face ofa mechanical seal on one hand, and friction coefficient of the sealingface on the other, obtained at each sliding speed of the sealing face.

MODES FOR CARRYING OUT THE INVENTION

Modes for carrying out a sliding component pertaining to the presentinvention are explained in detail by referring to the drawings, but itshould be noted that the present invention should not be interpreted ina limited way according to these embodiments alone, and variousmodifications, corrections and improvements may be added based on theknowledge of those skilled in the art so long as they do not deviatefrom the scope of the present invention.

The sliding component pertaining to an embodiment of the presentinvention is explained by referring to FIGS. 1 to 4.

As shown in FIG. 1 (a), a sliding component 1 constitute a ring-shapedbody and normally high-pressure sealed fluid is present on one side ofthe inner/outer peripheries of the sealing face S of the slidingcomponent 1, while atmosphere is on the other side.

This sealed fluid can be effectively sealed using the sliding component1. For example, this sliding component 1 is used as one of the pairs ofseal ring for rotation and seal ring for fixing in mechanical sealdevices. The sealing face of the seal ring for rotation is contactedwith the sealing face of the seal ring for fixing facing the seal ringfor rotation, to seal the sealed fluid present on either the innerperiphery or outer periphery of the sealing face. The sliding componentcan also be used as a bearing that slides against its rotating axiswhile sealing lubricating oil on one side of the cylindrical sealingface in the axial direction.

In FIG. 1, a case where high-pressure sealed fluid is present on theouter periphery side is explained for the sake of convenience.

In the illustrated example, the cross section of the sliding component 1has a convex shape as shown in FIG. 1 (c) and its top face constitutes asealing face S. This sealing face S has multiple positivepressure-generating mechanisms provided on it independently in thecircumferential direction, which are running roughly in parallel withthe sealing face S and constituted by extremely shallow parallel grooves2 having submicron-level height differences, as shown in FIG. 1 (b). Theextremely shallow parallel grooves 2 are provided not over the entirewidth of the sealing face S in the diameter direction, but only in anarea closer to the high-pressure fluid side, and connect to thehigh-pressure fluid side, while being isolated from the low-pressurefluid side by a seal area 3. This seal area 3 has such properties thatit achieves good lubrication characteristics but increases the chancesof leakage when narrow in the diameter direction, and decreases thechances of leakage but achieves poor lubrication characteristics whenwide in the diameter direction.

As shown in FIG. 1 (b), extremely shallow thin grooves 10 are formed atthe bottom of the extremely shallow parallel grooves 2. The extremelyshallow thin grooves 10 are provided to control the flow of fluid in theextremely shallow parallel grooves 2, and are formed in a specifieddirection. Additionally, the extremely shallow thin grooves 10 have asection shape of roughly a square groove in FIG. 1 (b), but the sectionshape is not at all limited to the foregoing and a wave shape orsaw-tooth blade shape is also acceptable, for example. At the bottom ofthe extremely shallow parallel grooves 2 before the extremely shallowthin grooves 10 are formed on them, its roughness is such that thesurface irregularity is approx. one-tenth the depth of the extremelyshallow parallel grooves 2, and the extremely shallow thin grooves 10are formed in the depth direction from this relatively smooth bottom.

The extremely shallow parallel grooves 2 have their depth h set in arange of 10 nm to 1 μm or preferably in a range of 50 to 500 nm.

The extremely shallow thin grooves 10 have their depth a set in a rangeof 10 nm to 1 μm and pitch p set in a range of 1 to 500 μm. Also, thewidth b of the extremely shallow thin grooves 10 is equal to or lessthan the pitch p.

Now, the “positive pressure-generating mechanisms constituted byextremely shallow parallel grooves” under the present invention areexplained.

Because the extremely shallow parallel grooves 2 constituting thepositive pressure-generating mechanisms are extremely shallow,represented by their depth h in a range of 10 nm to 1 and also becausethe extremely shallow thin grooves 10 are formed at their bottom and noprojections are present in the extremely shallow parallel grooves 2, thesealed fluid entering the extremely shallow parallel grooves 2 forms anextremely thin fluid film and the action of its surface tensionincreases the pressure region where the fluid can be sealed withoutincreasing leakage. In the rotation phase, dynamic pressure generates asa result of the applicable sealing face sliding relative to the matingsealing face and the sealing face can be lifted by the dynamic pressureeffect.

How dynamic pressure generates as a result of the applicable sealingface sliding relative to the mating sealing face and the sealing face islifted by the dynamic pressure effect during the rotation phase isexplained in detail by referring to FIG. 2.

As shown in FIG. 2 (a), under the present invention the extremelyshallow parallel grooves 2 are extremely shallow and also the extremelyshallow thin grooves 10 are formed at their bottom and no projectionsare present in the extremely shallow parallel grooves 2, andconsequently the dynamic pressure generating as a result of theapplicable sealing face sliding relative to the mating sealing face hasa large pressure distribution.

In the case of prior art, on the other hand, the dynamicpressure-generating grooves are formed in such a way that the height isroughly the same as the depth of the grooves, as shown in FIG. 2 (b),and therefore the dynamic pressure generating as a result of theapplicable sealing face sliding relative to the mating sealing face hasa smaller pressure distribution compared to that under the presentinvention.

As mentioned above, under the present invention the extremely shallowparallel grooves 2 are extremely shallow and therefore any leakage atstartup or stop is kept to a minimum, and while extremely shallow, theextremely shallow parallel grooves 2 have the extremely shallow thingrooves 10 formed at their bottom and have no projections inside andtherefore can exhibit the lubrication effect in the rotation phase.

Also, preferably the extremely shallow parallel grooves 2 are providedto account for 5 to 70% of the area of the sealing face S. While theextremely shallow parallel grooves 2 are equally distributed at 16locations in the circumferential direction in the illustrated example,their distribution is not at all limited to the foregoing and itsuffices that they are equally distributed at two locations at aminimum, for example.

The sealing face S itself is set, by mirror-surface finishing, to alevel of roughness at which the extremely shallow parallel grooves 2become clearly recognized.

Next, the “extremely shallow thin grooves” under the present inventionare explained.

The extremely shallow thin grooves 10 are provided to control the flowof fluid in the extremely shallow parallel grooves 2, and by setting theextremely shallow thin grooves in a desired direction, taking the fluidinto the extremely shallow parallel grooves 2 or discharging the fluidfrom the extremely shallow parallel grooves 2 can be made easier, orsupplying the fluid to the sealing face S can be made easier.

In other words, the extremely shallow thin grooves 10 formed at thebottom of the extremely shallow parallel grooves 2 control the flow offluid in the extremely shallow parallel grooves 2 and, for example, byrectifying the flow of fluid in the extremely shallow parallel groovesin an optimal direction according to the wideness or narrowness of theseal area formed between the extremely shallow parallel grooves andinner periphery of the seal area, sufficient design flexibility toachieve both improved lubrication characteristics of the sealing faceand reduced leakage can be realized, which has been difficult to do withthe extremely shallow parallel grooves 2 alone.

These extremely shallow parallel grooves 2 and extremely shallow thingrooves 10 at their bottom are processed by means of etching, forexample. However, the method is not at all limited to etching and anyother processing method may be used so long as the processed grooveshave their depth h in a range of 10 nm to 1 μm and extremely shallowthin grooves can be processed at the bottom.

Next, the extremely shallow thin grooves 10 are explained in detail byreferring to FIG. 3.

The extremely shallow thin grooves 10 are provided to control the flowof fluid in the extremely shallow parallel grooves 2, and formed in aspecific direction.

In FIG. 3 (a), the extremely shallow thin grooves 10 in each extremelyshallow parallel groove 2 are formed in a manner inclined by a specifiedangle relative to the sliding direction of the sealing face, orspecifically by a 45-degree angle relative to the centerline runningthrough the center of each extremely shallow parallel groove 2 from thecenter O of the sliding component 1, for example, and all extremelyshallow thin grooves 10 are formed in the same direction. As a result,when the mating sealing face rotates in the clockwise direction, thefluid in the extremely shallow parallel grooves 2 is rectified to flowto the high-pressure fluid side and consequently fluid leakage can bereduced even when the seal area 3 formed between the extremely shallowparallel grooves 2 and inner periphery of the seal area 3 is narrow.

In FIG. 3 (b), the extremely shallow thin grooves 10 in each extremelyshallow parallel groove 2 are formed in such a way that the adjacentextremely shallow thin grooves are inclined in directions symmetricalrelative to the sliding direction of the sealing face. As a result,fluid is rectified alternately to the high-pressure fluid side orlow-pressure fluid side in the adjacent extremely shallow parallelgrooves 2. Accordingly, the foregoing is advantageous when the slidingcomponent rotates in both directions.

In FIG. 3 (c), the extremely shallow thin grooves 10 in each extremelyshallow parallel groove 2 are formed along the diameter direction(direction parallel with the centerline running through the center ofeach extremely shallow parallel groove 2 from the center O of thesliding component 1, which is referred to as the “diameter direction” inthis Specification). As a result, fluid is rectified to flow in thediameter direction in the extremely shallow parallel grooves 2.Accordingly, fluid flows into the extremely shallow parallel grooves 2with ease even at startup or stop of the sliding component, andconsequently the lubrication characteristics at startup or stop of thesliding component can be improved. From the viewpoint of preventingleakage, the foregoing is suitable when the seal area 3 formed betweenthe extremely shallow parallel grooves 2 and inner periphery of the sealarea is wide.

In FIG. 3 (d), the extremely shallow thin grooves 10 in each extremelyshallow parallel groove are formed along the circumferential direction(direction orthogonal to the centerline running through the center ofeach extremely shallow parallel groove 2 from the center O of thesliding component 1, which is referred to as the “circumferentialdirection” in this Specification). As a result, fluid is rectified toflow in the circumferential direction in the extremely shallow parallelgrooves 2. Accordingly, fluid is supplied more easily when the slidingcomponent rotates, especially to the sealing face S positioned betweenthe extremely shallow parallel grooves 2, resulting in furtherimprovement of lubrication characteristics. From the viewpoint ofpreventing leakage, the foregoing is suitable when the seal area 3formed between the extremely shallow parallel grooves 2 and innerperiphery of the seal area is narrow.

The operations and effects of the sliding component in the embodiment ofthe present invention are as follows:

Because the extremely shallow parallel grooves 2 constituting thepositive pressure-generating mechanisms are extremely shallow, and alsobecause the extremely shallow thin grooves 10 are formed at their bottomand no projections are present in the extremely shallow parallel grooves2, the sealed fluid entering the extremely shallow parallel grooves 2forms an extremely thin fluid film and the action of its surface tensionincreases the pressure region where the fluid can be sealed withoutincreasing leakage. In the rotation phase, dynamic pressure generates asa result of the applicable sealing face sliding relative to the matingsealing face and the sealing face is lifted by the minimum requiredamount due to the dynamic pressure effect. Additionally, the extremelyshallow thin grooves 10 are formed at the bottom of the extremelyshallow parallel grooves 2 and therefore the flow of fluid in theextremely shallow parallel grooves 2 can be controlled and, for example,by rectifying the flow of fluid in the extremely shallow parallelgrooves in an optimal direction according to the wideness or narrownessof the seal area formed between the extremely shallow parallel groovesand inner periphery of the seal area, sufficient design flexibility tosimultaneously achieve improved lubrication characteristics of thesealing face and reduced leakage can be achieved.

Also, the extremely shallow parallel grooves 2 have their depth h set ina range of 10 nm to 1 μm or preferably in a range of 50 to 500 nm, whilethe extremely shallow thin grooves 10 have their depth h set in a rangeof 10 nm to 1 μm and pitch p set in a range of 1 to 500 μm, thelubrication characteristics at startup or stop can be improvedsignificantly without increasing leakage.

Also, the extremely shallow thin grooves 10 in each extremely shallowparallel groove 2 are formed in a manner inclined by a specified anglerelative to the sliding direction of the sealing face, or specificallyby a 45-degree angle relative to the centerline running through thecenter of each extremely shallow parallel groove 2 from the center O ofthe sliding component 1, for example, and all extremely shallow thingrooves 10 are formed in the same direction, and accordingly the fluidin the extremely shallow parallel grooves 2 can be rectified to flow tothe high-pressure fluid side and consequently the lubricationcharacteristics at startup or stop can be further improved significantlywithout increasing leakage, even when the seal area formed between theextremely shallow parallel grooves and inner periphery of the seal areais narrow.

Also, the extremely shallow thin grooves 10 in each extremely shallowparallel groove 2 are formed in such a way that the adjacent extremelyshallow thin grooves are inclined in the directions symmetrical relativeto the sliding direction of the sealing face, and accordingly fluid isrectified alternately to the high-pressure fluid side or low-pressurefluid side in the adjacent extremely shallow parallel grooves 2, whichis advantageous when the sliding component rotates in both directions.

Also, the extremely shallow thin grooves 10 in each extremely shallowparallel groove 2 are formed along the diameter direction and thereforefluid is rectified to flow in the diameter direction in the extremelyshallow parallel grooves, and accordingly fluid flows into the extremelyshallow parallel grooves with ease even at startup or stop of thesliding component, and consequently the lubrication characteristics atstartup or stop of the sliding component can be improved. From theviewpoint of preventing leakage, the foregoing is suitable when the sealarea formed between the extremely shallow parallel grooves and innerperiphery of the seal area is wide.

Also, the extremely shallow thin grooves 10 in each extremely shallowparallel groove 2 are formed along the circumferential direction andtherefore fluid is rectified to flow in the circumferential direction inthe extremely shallow parallel grooves 2, and accordingly fluid issupplied more easily at startup or stop of the sliding component or inthe rotation phase, especially to the sealing face S positioned betweenthe extremely shallow parallel grooves 2, resulting in furtherimprovement of lubrication characteristics. From the viewpoint ofpreventing leakage, the foregoing is suitable when the seal area formedbetween the extremely shallow parallel grooves and inner periphery ofthe seal area is narrow.

The foregoing explained embodiments of the present invention usingdrawings, but it should be noted that specific constitutions of thepresent invention are not at all limited to these embodiments, and anymodifications and additions thereto are also included in the scope ofthe present invention so long as they do not deviate from the key pointsof the present invention.

In the aforementioned embodiment, for example, an example of using thesliding component for one of the pairs of seal ring for rotation andseal ring for fixing in mechanical seal devices was explained, but thesliding component can also be used as a bearing that slides against itsrotating axis while sealing lubricating oil on one side of thecylindrical sealing face in the axial direction.

Also the an aforementioned embodiment, a case where high-pressure sealedfluid is present on the outer periphery side was explained, for example,but the present invention can also be applied when high-pressure fluidis present on the inner periphery side, in which case the extremelyshallow parallel grooves can be provided in a manner connected to theinner periphery side.

REFERENCE SIGNS

-   -   1 Sliding component    -   2 Extremely shallow parallel groove    -   3 Seal area    -   10 Extremely shallow thin groove    -   S Sealing face

1. A sliding component characterized in that: on one sealing face of apair of sliding parts that slide relative to each other, multiplepositive pressure-generating mechanisms that comprise extremely shallowparallel grooves running roughly in parallel with a sealing face andhaving submicron-level height differences are provided independently ina circumferential direction; the extremely shallow parallel groovesconnect to a high-pressure fluid side, but are isolated from alow-pressure fluid side by a seal area; and extremely shallow thingrooves are formed at a bottom of the extremely shallow parallelgrooves.
 2. A sliding component according to claim 1, characterized inthat the extremely shallow parallel grooves have a depth h of 10 nm to 1μm, while the extremely shallow thin grooves have a depth a of 10 nm to1 μm and pitch p of 1 to 500 μm.
 3. A sliding component according toclaim 2, characterized in that preferably the extremely shallow parallelgrooves have a depth h of 50 to 500 nm.
 4. A sliding component accordingto claim 1, characterized in that the extremely shallow thin grooves areformed in a manner inclined by a specified angle relative to a slidingdirection of the sealing face.
 5. A sliding component according to claim4, characterized in that the extremely shallow thin grooves are formedin such a way that adjacent extremely shallow thin grooves are orientedsymmetrical to a sliding direction of the sealing face.
 6. A slidingcomponent according to claim 1, characterized in that the extremelyshallow thin grooves are formed along a diameter direction.
 7. A slidingcomponent according to claim 1, characterized in that the extremelyshallow thin grooves are formed along a circumferential direction.
 8. Asliding component according to claim 1, characterized in that preferablythe extremely shallow parallel grooves are provided to account for 5 to70% of an area of the sealing face.
 9. A sliding component according toclaim 1, characterized in that the pair of sliding parts is comprised ofring-shaped bodies each used as either a stationary-side sliding memberor rotating-side sliding member of a mechanical seal that rotatesrelative to the other member.
 10. A sliding component according to claim2, characterized in that the extremely shallow thin grooves are formedin a manner inclined by a specified angle relative to a slidingdirection of the sealing face.
 11. A sliding component according toclaim 2, characterized in that the extremely shallow thin grooves areformed along a diameter direction.
 12. A sliding component according toclaim 2, characterized in that the extremely shallow thin grooves areformed along a circumferential direction.
 13. A sliding componentaccording to claim 2, characterized in that preferably the extremelyshallow parallel grooves are provided to account for 5 to 70% of an areaof the sealing face.
 14. A sliding component according to claim 2,characterized in that the pair of sliding parts is comprised ofring-shaped bodies each used as either a stationary-side sliding memberor rotating-side sliding member of a mechanical seal that rotatesrelative to the other member.
 15. A sliding component according to claim3, characterized in that the extremely shallow thin grooves are formedin a manner inclined by a specified angle relative to a slidingdirection of the sealing face.
 16. A sliding component according toclaim 3, characterized in that the extremely shallow thin grooves areformed along a diameter direction.
 17. A sliding component according toclaim 3, characterized in that the extremely shallow thin grooves areformed along a circumferential direction.
 18. A sliding componentaccording to claim 3, characterized in that preferably the extremelyshallow parallel grooves are provided to account for 5 to 70% of an areaof the sealing face.
 19. A sliding component according to claim 3,characterized in that the pair of sliding parts is comprised ofring-shaped bodies each used as either a stationary-side sliding memberor rotating-side sliding member of a mechanical seal that rotatesrelative to the other member.
 20. A sliding component according to claim4, characterized in that preferably the extremely shallow parallelgrooves are provided to account for 5 to 70% of an area of the sealingface.